1. Field of the Invention
The embodiments described herein relate generally to the field of video display control, and more particularly to the dynamic knee point determination of soft clipping based on backlight dimming ratio.
2. Description of Related Art
Backlight dimming is an extensively used technique in the field of video display control. Energy resource preservation and efficient power consumption management of consumer electronic (CE) devices have led to the incorporation of mechanisms that dim backlights illuminating display images. Backlight dimming may be triggered by certain environmental conditions, or other usage parameters that may allow a video display to function properly without using its maximum power capabilities. In this manner, a reduced power consumption may be realized, leading to longer battery lifetimes (e.g. in the case of laptop computers), less device heating, and overall reduced operation cost of CE devices. One of the challenges faced by designers using backlight dimming is maintaining the quality of the video image displayed under different backlight intensities.
In the case of video displays that make use of liquid crystal (LC) panels, controlling backlight intensity levels may be complemented with control of the LC layer transparency. However, systems currently available commercially provide a simple boost of the transparency of the LC layer. Then, current techniques combine transparency boost with a clipping of pixel transparency once the maximum digital range has been achieved. Thus, commercially available systems present portions of the image having the brightest level attainable, loosing any detail and contrast in those portions, with the consequent loss of image quality. Moreover, the clipping level of the pixel intensity may be fixed for all values of backlight dimming and all contrast conditions of the image being processed. For a video signal streaming multiple frames this may result in a video with varying degree of image quality, which is not desirable.
In order to avoid this problem, some designs provide image-dependent algorithms to regulate the degree of transparency for each pixel according to the particular conditions of an image. This may be achieved by optimizing an image quality factor pixel-to-pixel by comparing the input image with the backlight adjusted image. However, these image-dependent mechanisms involve complex calculations performed for every frame being transferred to the display system. The result is a limited time response for image adjustment, which is not desirable for a video transmission. Furthermore, such configurations need to implement complex algorithms using sophisticated memories and processor chips.
What is needed is a method and an apparatus to compensate for backlight dimming in video displays and maintain the quality of the image being displayed. Furthermore, it is desirable that the method be simple, fast to implement, and dynamically adjustable to different backlight levels.